Process and bath for depositing ruthenium



' nium coatings.

Patented ()ct. 13, 1936 UNITED STATES PATENT OFFICE PROCESS AND BATH FOR DEPOSITING BUTHENIUM No Drawing. Application January 16, 1935, Serial No. 2,050

13 Claims.

This invention relates to methods of and baths for electroplating ruthenium.

An object of this invention is to deposit smooth and adherent coatings of ruthenium. Ruthenium is a metal of the platinum group. It is white in color and very resistant to oxidation and atmospheric conditions. The metal is unaffected by mineral acids. The electrodeposited ruthenium closely resembles the color of rhodium and in many instances may be substituted therefor. Also within the contemplation of our invention is the use of baths or electrolytes for depositing alloys of ruthenium with any of the other platinum metals or with other metals.

The ruthenium coatings or deposits may be used to protect tarnishable metal surfaces, such as silver or the like, which results in tarnishproofing the cheaper metals. Also ruthenium may be deposited on non-tarnishing surfaces, such as jewelry, watch cases and similar articles, where a durable white surface is desired. Using our invention we can deposit thin or heavy ruthe- Furthermore, non-metallic articles, such as, carbon and graphite, may be plated with ruthenium according to our invention. In some instances, also, it may be advisable to plate the metal with some other covering metal such as nickel or copper before plating with ruthenium to form an underplating of such metal or metals.

Further advantages and features of our invention will be in part obvious and in part specifically pointed out in the description hereinafter contained, which discloses several embodiments of our invention, it being expressly understood, however, that various changes may be made in practice within the scope of the appended claims without digressing from our inventive idea.

We have found that broadly, aqueous solutions of ruthenium compounds containing the nitroso (NO) group form valuable electroplating solutions. These compounds may be used in acid, alkaline or neutral baths for plating. More particularly we have found that aqueous solutions of ruthenium compounds containing the nitroso (N0) group and also the ammino (NHs) group may be used in acidic, alkaline or neutral condition to electroplate ruthenium. Instead of the ammino group we may substitute the radicals of organic bases, such as pyridine, or the like. The pH range of the baths is from 1 to 14. All of these plating solutions or baths are very stable and the plating efliciency stays substantially the same for several months. Other examples given in the specification broadly show ruthenium electroplating solutions and also additional examples show ruthenium electroplating solutions containing substituted ammino compounds.

The following examples for the deposition of ruthenium are given. It is to be expressly understood that we are not to be limited to the examples given in the specification, as the proportions and conditions may be varied within limits without departing from the spirit of our invention.

Ruthenium nitroso hydroxide [RuNO(OH)3.- H2O] was dissolved in hydrochloric acid to form ruthenium nitroso chloride [RllNOClsl-IzO] This compound was dissolved in several acids and electroplating baths were made up as set forth below. Ruthenium was deposited from these baths under the following conditions using brass sheet cathodes of 1" x 3 and good platings were obtained. In the examples, amperes per square decimeter are given.

Ruthenium nitroso chloride [RuNOChHzO] ;gm 1

Sulphuric acid cc 5 Water cc 250 Ruthenium nitroso chloride [RllNOChHzO] .-gm 1 Phosphoric acid (H3PO4) cc 10 Water cc 250 The plating was done at 5 volts and 2.21 amperes per square decimeter, at 75 C. for 2 minutes.

Ruthenium nitroso chloride [RllNOCh-HaO] gm 1 Hydrochloric acid cc 5 Water cc 250 The plating was done at 2.75 volts and 2.21 amperes per square decimeter, at 66 C. for 2 minutes. I

Ruthenium nitroso chloride [RUNOCI3.H2O] gm 1 Oxalic acid gms 5 Water cc 250 Plated at 4.5 volts and 2.21 amperes per square decimeter at 50 C. for 2 minutes.

It was found that the nitroso compounds are very smooth white deposit of ruthenium was obtained.

This is one of the preferred forms of bath using the nitroso compounds. Another example for plating ruthenium is as follows: Ruthenium nitroso chloride was prepared by dissolving 2.0i gms..

of ruthenium nitroso hydroxide in 30 cc. hydrochloric acid and a few drops of nitric acid were added and the solution evaporated to dryness. The salt was dissolved in 500 cc. of water and 10 cc. sulphuric acid were added. This bath was electrolyzed at 2 volts and 2.21 amperes per square decimeter for minutes at 65 C. and a bright and adherent deposit of ruthenium obtained.

An example using an acetate compound is as follows:

2 gms. ruthenium as ruthenium nitroso hydroxide were dissolved in 20 cc. of acetic acid and evaporated to dryness to remove excess acetic acid. The residue was dissolved in 500 cc. of water containing cc. of sulphuric acid. The resulting bath was electrolyzed at 75 C. at 2.2 volts, 2.21 amperes per square decimeter for 5 minutes and a bright and smooth deposit of ruthenium was obtained.

We have also deposited alloys of ruthenium and other precious metals of which the following is an example of a ruthenium-rhodium deposit:

3 gms. of ruthenium nitroso hydroxide (1.5 gm. ruthenium) were dissolved in 30 cc. of water containing 20 cc. of sulphuric acid, and the solution was diluted to one liter. To this solution was added 1 gm. of rhodium as rhodium phosphate. The solution was electrolyzed for 5 minutes at 43 C. and 2.5 volts and 2.21 amperes per square decimeter. A bright and adherent deposit of an alloy of rhodium and ruthenium was obtained.

Ruthenium-platinum alloy deposits may be obtained from the following alkaline and acid baths:

1 gm. of ruthenium as ruthenium nitroso hydroxide [RuNO(OH)aH2O] and 1 gm. of platinum as platinum ammino nitrite [Pt(NH3)2(NO2)2] were dissolved in 100 cc. of boiling NHrOH and diluted with water to 500 cc. This solution was electrolyzed at 75 C. and 7.5 volts and 1.1 amperes per square decimeter and a bright deposit of an alloy of ruthenium and platinum was obtained.

An acid electrolyte was obtained and electro-* lyzed as follows:

1 gm. of ruthenium as ruthenium nitroso hydroxide [RuNO(OH) aHzO] and 1 gm. of platinum as platinum ammino nitrite [Pt(NHa)2(NO2)2] were dissolved in 500 cc. of water containing 10 cc. of sulphuric acid. This solution was electrolyzed at 55 C. and 2.2.volts and 2.21 amperes per square decimeter and a bright and smooth platinum-ruthenium deposit was obtained.

Ruthenium-palladium alloy deposits may be obtained from the following alkaline and acid baths: I

1 gm. of ruthenium as ruthenium nitroso hydroxide [RllNO(OH)aH20] and 1 gm. of palladium as palladium ammino nitrite were dissolved in 100 cc. oi boiling NHiOH and diluted with water to 500 cc. This solution was electrolyzed at 70 C. and 6.5 volts and 1.1 amperes per square decimeter and a palladium-ruthenium alloy deposit obtained.

1 gm. of ruthenium as ruthenium nitroso hydroxide [RUNO(OH)3H2O] and 1 gm. of palladium as palladium ammino nitrite [Pd(NH3) 2(NO2) 2] were dissolved in 500 cc. of water containing 10 cc. of sulphuric acid. This solution was electrolyzed at 45 C. and 2.3 volts and 2.21 amperes per square decimeter and a palladium-ruthenium alloy deposit was obtained. i

We have also plated ruthenium nitroso co pounds out of alkaline baths of which the following are examples:

1 gm. ruthenium as ruthenium nitroso hydroxide was dissolved in 40 cc. of water plus 10 gms. sodium hydroxide. This solution was diluted to 500 cc. and heated to 45 C. A current of 1 to 2 volts and 2.21 amperes per square decimeter was passed through the solution and a bright and adherent deposit of ruthenium obtained.

2 gms. of ruthenium as ruthenium nitroso sulfate were dissolved in 100 cc. of water and made alkaline with 10 gms. of sodium hydroxide dissolved in 100 cc. of water. The alkaline bath thus produced was diluted with water to one liter and electrolyzed for 5 minutes at 52 C. and 3 volts 'and 2.21 amperes per square decimeter and a good plating oi ruthenium was obtained.

2 gms. of ruthenium as ruthenium nitroso chloride were dissolved in 100 cc. of water and made alkaline with 10 gms. of sodium hydroxide dissolved in 100 cc. of water. The alkaline bath produced in this way was diluted with water to one liter and electrolyzed for 5 minutes at 41 C. and 3 volts and 2.21 amperes per square decimeter and a good plating of ruthenium obtained.

The following examples show the use of nitroso ammino compounds in ammoniacal solutions:

2 gms. of ruthenium as ruthenium nitroso hydroxide were dissolved in 100 cc. of boiling ammonium hydroxide. This forms the ruthenium nitroso ammino hydroxide. This solution was electrolyzed for 5 minutes at 70 C. and 8.5 volts, 1.1 amperes per square decimeter and a bright deposit of ruthenium obtained.

4 gms. of ruthenium nitroso hydroxide (50% Ru) were dissolved in 10 cc. of sulphuric acid and 100 cc. water. The solution was poured into ammonium hydroxide, containing 30 cc. excess ammonium hydroxide. In this way ruthenium nitroso ammino sulphate was formed. The solution was heated to 75 C. and electrolyzed at 2 volts and a plating obtained.

4 gms. of ruthenium nitroso hydroxide (50% Ru) were dissolved in 12 cc. of phosphoric acid and poured into ammonium hydroxide suificient for 30 cc. ammonium hydroxide excess. The solution was heated to 75 C. and electrolyzed at 2 volts and 2.21 amperes per square decimeter to obtain a ruthenium plating.

4 gms. of ruthenium nitroso hydroxide were dissolved in nitric acid and converted to the ammino nitrate as in the preceding examples and a good plating bath was obtained.

4 gms. of ruthenium nitroso hydroxide were dissolved in hydrochloric acid and converted to the ammino chloride with 30 cc. excess of ammonium hydroxide and diluted to 500 cc. with water. A bright deposit of ruthenium was obtained when the-solution was electrolyzed at 2 volts and 2.21 amperes per square decimeter at 75 C. This plating bath is one of the preferred embodiments of our invention with baths using a nitroso ammino compound.

The following examples show the use of ruthenium nitroso ammino compounds in alkaline solution for electroplating or electrodeposit- I ing ruthenium 2 gms. of ruthenium as ruthenium nitroso ammino sulfate were dissolved in one liter of water and made alkaline with 1 gm. of sodium hydroxide. The solution so formed was electrolyzed at 30 C. for 5 minutes at 8.5 volts and 2.21

amperes per square decimeter and a good deposit All electrolytes in this table were diluted with water to one liter and contained 4 gms. of ruthenium as ruthenium nitroso hydroxide dissolved in the acids given in the table, the amounts of the acids being given per liter of solution. All these electrolytes gave deposits of ruthenium. In the last three examples sulphuric acid and conducting salts were added as given in the table. Other conducting salts may be used and further conducting salts may be added to any of the solutions given in Table I. The examples given are not the only ones which will work, but the results obtained indicate that the invention includes other similar compounds than those given and we are not to be restricted only to the examples given. These remarks also apply to the other tables herein given and also to the other examples set forth.

T Amperes emperper Acid per liter ature Volts Square decimeter 20 (:0. 57 2. 2 2. 21 40 cc. 70 3.0 2. 21 20 cc. 27 3. 5 2. 21 20cc. 65 2.8 4.42 20 cc. 26 2. 8 2. 21 20 cc. 30 4. 0 2. 21 20 cc. 10 5.0 2. 21 20 grams oxalic acid 70 3. 5 2. 21 40 cc. acetic ac 75 8.6 664 grams tartaric acid 5. 4 2. 87 80 grams citric acid 75 6. 4 2. 21 40 cc. lactic ac 75 3.5 .664 40 cc. formic acid 85 6.0 2. 21 40 cc. hydrofluosilicic acid 90 2. 1 2. 21 40 cc. hydrofluosilicic acid 37 2. 6 2. 21 40 cc. phosphoric acid (20 cc. sulfuric acid added) 60 2.2 2. 21 20 cc. hydrochloric acid (10 gms. am-

monium chloride added) 25 3.0 2. 21 20 cc. nitric acid (10 gms. ammomum nitrate added) 65 2. 8 4. 42

Table II For this work acid solutions of ruthenium nitroso hydroxide were made ammoniacal to form ammino nitroso ruthenium salts. All these electrolytes of Table II contain 4 gms. of ruthenium per liter.

T Ampere.

emperper ature volts square decimeter Ruthenium nitroso ammino sulfate C' 30 gins. ammonium suliate 85 3. 5 4.42 Ruthenium nitroso ammino nitrate 20 ms. ammonium nitrate..-.-.. 83 3. 6 4. 42 Ruthe um nitroso ammino chloride 36 gms. ammonium chloride. 85 2. 8 4.42 Ruthenium nitroso ammino phosphate 27 gins. ammonium phosphate-.- 90' 4. 0 15.47 Ruthenium nitroso ammino bromide 2 gms. ammonium bromide 75 4.2 4. 42 Ruthenium nitroso ammino oxalate 37 gms. ammonium oxalate 90 5. 5 4. 42 Ruthenium nitroso ammino acetate 44 gms. ammonium acetate 75 4. 6 4. 42 Ruthenium nitroso ammino tart-rate 87 gms. ammonium tartrate 75 3. 0 4. 42 Ruthenium nitroso ammino citrate 92 gms. ammonium citrate 77 3. 2 4. 42 Ruthenium nitroso ammino lactate 36 gms. ammonium lactate 78 8. 6 4.42 Ruthenium nitroso ammino iormate 40 gms. ammonium iormate 75 3. 8 4. 42 Ruthenium nitroso ammino fluosilieate .5 gms. ammonium fiuoride.. 75 4. 6 4.42

In Table II the simple ammonium salts are formed when the acid solutions of the ruthenium nitroso compounds are made ammoniacal. These ammonium salts act as conducting salts or agents. Of course, we are not to be restricted to ammonium salts as the conducting agents as other salts or compounds may be used. It is not absolutely necessary to have conducting salts present in the solutions and we may use the ammino nitroso compounds alone in ammoniacal solution without conducting salts. In general when conducting salts are added lower voltages and amperages may be used.

' Table III The electrolytes made up as given in Table II were boiled to remove ammonia until the electrolytes were neutral and electrodeposition of ruthenium was efiected from solutions of neutral ruthenium ammino nitroso salts of the acids as given below. The solutions contained 4 gms. of ruthenium as nitroso ammino salts.

The solutions or electrolytes made up as given in Table III were acidified with their respective acids and electrolyzed as shown below and electrodeposition of ruthenium was obtained.

T Amperea emper- P 1 liter electrolyte 8mm Volts Square decimeter 5 cc. sulfuric acid added 74 3. 0 3. 87

5 cc. nitric acid added 71 2. 8 3. 87

5 cc. hydrochloric acid added. 75 2. 8 3. 87

10 cc. phosphoric acid added... 75 3. 0 3.87

It will be noted that Tables III and IV do not contain all the compounds set forth in Table II. The other compounds given in Table II may also be treated in the way set forth in connection with Tables 1121 and IV and electrolytes obtained from which ruthenium may be deposited. Conducting salts may be used if desired but are not absolutely necessary. I

The following additional examples show ruthenium baths for electroplating made by other methods.

' Gms. Potassium hydroxide 10 Potassium nitrate 3 Ruthenium metal 1 This mixture was fused for one hour in a gold dish. We believe that the compound formed by this fusion contains a nitroso group. The fusion was dissolved in water and diluted to one liter with water. The solution was electrolyzed for 5 minutes at 30 C., at 7.5 volts and 2.21 amperes per square decimeter and a good deposit of ruthenium was obtained.

Gms. Potassium hydroxide Potassium nitrate 3 Ruthenium metal 1 This mixture was fused for one hour in a gold dish, then dissolved in water and neutralized with 50% phosphoric acid. A precipitate was formed which was filtered out, washed and dissolved in 20 cc. of phosphoric acid at 350 C. This solution was diluted to one liter with water and electrolyzed and a good deposit of ruthenium was obtained.

An example of a solution for electroplating ruthenium showing the use of pyridine is given below.

1 gm. of ruthenium as ruthenium nitroso chloride in 50 cc. of water was treated with 3.2 gms. of pyridine in 100 cc. of water. The solution was diluted with water up to 500 cc. and 10 cc. of sulfuric acid added. The solution was electrolyzed for 5 minutes at 48 C. and 2.3 volts and 2.21 amperes per square decimeter and a bright deposit of ruthenium was obtained.

Another example of .a solution for electroplating or electrodepositing ruthenium including ethylenediamine is as follows:

1 gm. of ruthenium as ruthenium nitroso chloride was dissolved in 10 cc. of water and treated with 2.6 gm. of ethylenediamine. The solution was diluted with water up to 500 cc. and then 10 cc. of sulfuric acid. The solution was electrolyzed for 5 minutes at 61 C. and 2.2 volts and 2.21 amperes per square decimeter and a bright deposit of ruthenium was obtained.

Instead of ethylenediamine we may use other amine compounds such as triethanolamine. Also derivatives and homologs of pyridine and the amine compounds maybe used.

What we claim is:

1. A process for electroplating bright and lustrous ruthenium for decorative or protective purposes, which comprises passing a direct current of about 1 to 3 volts and about 2 to 4.5 ampjdm. through an electrolyte which maintains its stability and plating efliciency over an extended pe'- riod of time, said electrolyte containing about 4 gm. of ruthenium per liter as a ruthenium nitroso compound.

2. A process for electroplating ruthenium, which comprises passing a current through an electrolyte containing a ruthenium nitroso compound, the pH of the electrolyte ranging from about 1 to about 14.

3. A process for electroplating ruthenium, which comprises passing a current through an electrolyte containing a ruthenium nitroso amino compound, the pH of the electrolyte ranging from a about 1 to about 14.

4. A process for electrodepositing ruthenium which comprises passing a current of about 3 volts and about 2 amperes per square decimeter through an electrolyte containing ruthenium nitroso sulphate, and maintaining the temperature of the electrolyte at about 60 C.

5. A process for electrodepositing ruthenium which comprises passing a current of about 2 volts and about 2 amperes per square decimeter through an electrolyte containingruthenium nitroso ammino chloridepand maintaining the temperature of the electrolyte at about 75 C.

6. An electrolyte for plating ruthenium which contains ruthenium nitroso sulphate.

'7. An electrolyte for plating ruthenium which contains ruthenium nitroso ammino chloride.

8. An electrolyte for plating a rutheniumrhodium alloy which contains a ruthenium nitroso compound and a rhodium compound.

9. An electrolyte for plating ruthenium which includes a solution of a ruthenium compound containing a nitroso group.

10. An electrolyte for plating ruthenium which comprises a solution containing an amino or organic base derivative of a ruthenium compound containing a nitroso group.

11. An electrolyte for electroplating ruthenium which contains a productformed by fusing ruthenium metal with an alkali and an alkali nitrate.

12. An electrolyte for electroplating ruthenium which is formed by fusing ruthenium metal with potassium hydroxide and potassium nitrate and dissolving the fusion in water.

13. A process for plating an alloy of ruthenium and one or more platinum metals, which comprises passing a current through an electrolyte FRITZ ZIMMERMANN. HERBERT EMIL ZSCHIEGNER. 

